Rotary compressor



Oct. 14 1924. 1,511,468

- E. HILL ROTARY COMPRES S OR Filed Oct. 26, 1923 2 Sheets-Sheet 1INVENTOR Wig/L,

ATTORNEY Oct. 14 1924. 1,511,468

E. HILL ROTARY COMPRESSOR Filed Oct. 26. 1923 2 Sheets-Sheet 2 INVENTORM \/M A! TLIORNE Y Patented Oct. 14, 1924.

UNITED STATES I 1,511,468 PATENT OFFICE.

EBENEZER 'HIIJL, OF SOUTH NORWALK, CONNECTICUT, ASSIGNOR TO THE HILLCOM- PRESSOR & PUMP COMPANY, OF NEW YORK, N. Y., A CORPORATION OFDELAWARE.

ROTARY COMPRESSOR.

Application filed October 26, 1923. Serial No. 670,898.

To all whom it"may concern: 4

Be it known that I, EBENEZER HILL, a citizen of the United States,residing at South 'Norwalk, in the county of F airfield 5 and State ofConnecticut, have invented a new and useful Improvement in RotaryCompressors, of which the following is'a specification.

This invention relates to motor driven rotary fluid compressors of thetype in which there is a rotor connected with-and driven by the armatureshaft of an electric motor, which rotor contains and actuates twointermeshing pumping gears that are held in engagement with a wall ofthe pumping chamber so that the fluid being pumped will not leak acrossthe faces of the gears, primarily, as on starting, by a light spring,but when in operation, by the excess discharge pressure of the fluidpumped exerted against the back of the rotor. In compressors of thischaracterwhen there is merely atmospheric pressure on both the intakeand discharge sides, the rotor is held against the wall of the pumpingchamber by the tension of the spring back of the rotor, with onlysufficient force to cause slight frictional engagement, so that themotor starts the comressor easily. As the discharge pressure uilds upunder the action of the compressor,

the force on the back of the rotor increases and the sealing engagementof the rotor and gears with the wall of the pumping chamber iscorrespondingly increased. When the compressor is working the pressureon the opposite sides of the rotor is to an extent balanced there beinglittle more pressure on the back than the front, but this is notexcessive and therefore the friction is not great and the motor drivesthe com pressor easily.

When such a compressor 15 stopped with pressure on the discharge sidethat pressure as soon as the compressor starts and begins to pump thepressure on the front of the rotor increases to nearly that on the back,and the frictional engagement of the rotor and ears with the wall of thepumping chain er being thusreduced the motor runs with its normalfriction load. These factors make necessary the employment of arelatively large sized motor .and one that is especially built so as tohave a high starting torque, which will overcome the initial frictionalload when the compressor is stopped under pressure.

The object of the present invention is to provide equalizing meansvpreferably located on the intake side of the compressor, which willremain inactive when the pressure is atmospheric on both sides, or ispractically balanced on both sides of the rotor, as when the compressoris working, but will, if the 75 compressor is stopped with a highpressure on the discharge side, act to retain the pres-' sure on theintake side at substantially the same degree as on the discharge side,in order that the only friction of the rotor 1 and gears against thewall of the pumping chamber will be that due to the'action of; thespring. -.With the pressure thus in effect balanced, the motor willstart the compressor easily and without overload. As a' as result of theuse of this equalizing means a smaller and less expensive motor, with astandard starting torque, can be used, than is required when thecompressor is not provided with equalizing means. This effects aconsiderable saving in the initial cost of the apparatus and an economyin running expense.

This object is attained by arranging a valve on the intake side of thecompressor, desirably in the intake port in the head, in such mannerthat it offers no practical obstruction to the flow of fluid under thenormal operation of the compressor, but when the compressor is stoppedwith high pressure on the discharge side, and the fluld tends to leakback across the faces of the pumping gears, that leakage will cause thevalve to close the intake port and retain the fluid pressure on theintake side or front 105 faces of the rotor and gears substantially thesame as on the discharge side or back face of the rotor, thus reducingthe friction so that the compressor will again start without excessresistance to torque. The equalizing In the accompanying drawm s Figure1 shows a side view of a motor riven com- 1 pressor of the characterreferred to, with a portion of the compressor cut in longitudinalsection to disclose anequalizing means arranged in the intake port orthe head. Fig. 2 is a transverse section of the compressor on the planeindicated by the dotted hne 22 on Fig. 1. Fig. 3 is a transverse sectionon the plane indicated by the dotted line 33 on ig. 1.

The casing 1 which is generally circular in outline contains acylindrical pumping chamber 2 that is closed at one end by a head 3which is fastened to the casing by any suitable means. The casinghas anintake passage 4 on one side and a discharge passage 5 on the otherside, whlle the head has an intake port 6 leading from the intakepassage to the pumping chamber and a discharge port 7 leading from thepumping chamber to the discharge passage. Rotatably fitting and having aslight movement axially in the pumping chamber is a rotor 8. The hub 9of the rotor is mounted on antifriction bearings 10 the inner ring 11 ofwhich is fastened to the hub while the outer race ring 12 is fitted sothat it may have a slight axial movement in the casing. The drivingshaft 13 is splined in the hub of the rotor so that while the shaft willturn the rotor it will not interfere with the axial movement of therotor. Fastened in the ro-= tor is an internally toothed gear 1a andengaging the teeth of this gear are the teeth of -an externally toothedgear 15. The externally toothed gear is mounted on anti-frictionbearings 16 arranged in a cavity 17 in the gear and supported by a stud18 fastened in the head. The stud is positioned out of line with thedriving shaft so that the axis of the externally toothed gear will beeccentric with the axis of the internally toothed gear. One of thesegears has more teeth than the other and they coact in a well knownmanner to effect the pumping or compression of fluids.

A spring 19 is arranged in a cavity 20 that communicates with thepumping chamber, in such manner that it thrusts against the outer racering 12 and through the bearing presses the rotor and the faces of thepumping gears against the inner face of the head. Lubricant isintroduced into this cavity. Leading from the reservoir 21 into whichthe fluid is pumped, to the cavity containing the spring is a pipe 22.The function of thisconnection is to admit discharge pressure to thecavity and permit it to be exerted on the back of the rotor. Thisconnection also is adapted to conduct back lubricant which has beenforced through the joints of the pump and out through the dischargepipe. A. common type of gland packing 23 is arranged in the end of thecasing to prevent leakage from the spring cavity around the drivingshaft.

A duct or passage 2 is made throughthe hub of the rotor from thepressure cavity containing the spring back of the rotor, to the cavitycontaining'the bearing for the externally toothed gear in front of therotor. When the pump is runnin the centrifugal force of the externallytoot ed gear and the fact that it wipes around on the face of the headis sufficient to allow just the right amount of lubricant to work out onthe faces of the gears and also between the contacting faces of theteeth. The lubricant which escapes dpasses through the discharge and isreturne to the pressure chamber so as to furnish a,v continuous supplyof lubricant under pressure. v

In the apparatus illustrated the armature shaft of the electric motor 25is directly connected with and acts as the driving shaft for the rotorof the compressor. In order to accomplish the object of this inventionand enable the motor to start without excessive torque and overload, inthe apparatus shown,

a valve 26 is located in the head and is pressed by a light spring 27 soas to normally close the intake port. This valve and spring are locatedin a screw plug 28 threaded into the head opposite the intake port. Thevalve however could be placed at any convenient locality on the intakeside of the compressor.

When the compressor is started up and as it continues to run, theinrushing fluid to the pumping chamber overcomes the li ht tension ofthe spring and holds the equa izing valve open. As there are nopulsations in the compressor and the inrush of air is substantiallysteady the equalizing valve has no vibration. However when thecompressor is stopped with fluid pressure on the discharge side, theequalizing valve is closed by its spring because there is no enteringfluid to hold it open. Immediately this valve closes the pressure thatleaks back across the faces of the gear teeth from the dischargecavities into the intake cavities, as it cannot get past the equalizingvalve, it builds up until the pressure on both sides of the rotorbecomes equal. With the pressure balanced the only force tending to holdthe rotor and gears against the face of the head is that of the springin the cavity back of the rotor, and this being relatively light thefrictional resistance of the rotor and gears to the motor on startingwill be the same as if there was atmospheric pressure on both the intakeand discharge sides of the compressor. With this arrangement there is anadvantage in permitting a slight amount of leakage across the face ofthe gears. If the compressor is to start up and shortly stop, and thensoon start up again, automatical on a fluctuating cycle of pressurewhich requires it to start and stop quickly at various intervals, theamount of leakage could be increased somewhat, so that the pressure dueto the closing of the intake by the equalizing valve would act promptlyand the stabalizing of the pressure on the rotor be quickly effected, inorder that the motor be in condition to start at any time withoutexcessive over load. v

This pressure equalizing valve in the inlet has another advantageousfunction. Besides equalizing the pressure and allowing the motor tostart without ahigh starting torque, it ensures the same pressure atboth ends of the lubricating port through the rotor. This stops thelubricant flow as there is no excess pressure on the back to ,force itthrough the port on account of the pressure being the same on bothsides, and the rotation having ceased, there is no wiping effect of thegears to pass this lubricant along. Therefore in addition to making thestarting torque lighter the supply of lubricant is automatically stoppedand started with the compressor by the equalizing means.

The invention claimed is 1. A rotary compressor comprising a casingcontaining a pumping chamber with an intake to and a discharge from saidchamber, a rotor rotatable in and having an axial movement in saidchamber, intermeshing internal and external pumping gears rotated by andhaving an axial movement with said rotor, means for conducting dischargepressure to the back of the rotor for forcing the rotor and gears towardthe front end of the pumping chamber, and means on the intake sidepermitting an unrestricted flow of fluid to the front of the pumpingchamber but preventing the escape of fluid back from the pumping chamberso as to kee the pressure on the front of the rotor su tantially thesame as the discharge pressure on the back of the rotor when thecompressor is idle and thereby lower. the starting torque of thecompressor.

2. A rotary compressor comprising a casing containing a pumping chamber,a head closing the front end'of the pumping chamber, said head having anintake to and a discharge from said chamber, a rotor rotatable'in andhaving an axial movement in said chamber toward and from the head,intermeshing internal and external pumping gears rotated b and having anaxial movement with sai rotor, means for conducting discharge pressureto the back of the rotor for forcing the rotor and gears toward thehead, and means on the intake side permitting an unrestricted flow offluid to the front of the pumping chamber but preventing the escape offluid back from the pumping chamber so as to keep the pressure on thefront of the rotor substantially chamber, intermeshing internal andexternal pumping gears rotated by and having arr axial movement withsaid rotor, a spring in the cavity adapted to force the rotor and gearstoward the front of the pumping chamber, means for conducting dischargepressure to the back of the rotor for, with said spring, forcing therotor and gears toward the front of the pumping chamber, and means onthe intake side permitting an unrestricted flow of fluid to the front ofthe pumpin chamber but preventing the escape of uid back from thepumping chaimber so as to keep the fluid pressure on the front of therotor substantially the same as the fluid pressure on the back of therotor when the compressor is idle and thereby lower the starting torqueof the compressor.

4. A rotary compressor comprising a casing containing a pumping chamberwith an intake to and a discharge from said chamher, a rotor rotatablein and having an axial movement in said chamber, an electric motordirectly connected with and adapted to drive the rotor, intermeshinginternal and external pumping gears rotated by and having an axiamovement with said rotor, means for conducting discharge pressure to theback of the rotor for forcing the rotor and gears toward the front endof the pumping chamber, and means on the intake side permitting anunrestricted flow of fluid to the pumping chamber but preventing theescape of fluid back from the pumping chamber so as to keep the pressureon the front of the rotor substantially the same as on the back of therotor when the compressor is idle and thereby lower the start- I ingtorque of the compressor.

5.- A rotary compressor comprising a casing containing a pumping chamberwith an intake to and a discharge from said chamber, intermeshinginternal and external pumping gears rotated in and having an axialmovement in said chamber, means for conducting discharge pressure to theback of the gears for forcing the gears toward the front end of thepumping chamber, and means on the intake side permitting an unrestrictedflow of fluid to the front of the pumping chamber but preventing theeslower the starting torque of the compressor.

6. A rotary compressor comprising a cas ing containing a pumpingchamber, a head closing the front end of the pumping chamber, said headhaving an intake to and a discharge from said chamber, a rotor rotatablein and having an axial movement in said chamber toward and from thehead, intermeshing internal and external pumping gears rotated by andhaving an axial movement with said rotor, means for conducting dischargepressure to the back of the rotor for forcing the rotor and ge rs towardthe i head, and a valve in said head on the intake side permittinganunrestricted flow of fluid to the front of the pumping chamber butpreventing the escape of fluid back from the pumping chamber so as tokeep the pressure on the front of the rotor substantially the same asthe discharge pressure on the back of the rotor when the compressor isidle and thereby lower the starting torque of the compressor.

7. A rotary compressor comprising a casing containing a pumping chamberwith an intake to and a discharge from said chamber, a rotor rotatablein and having an axial movement in said chamber, intermeshing internaland external umping gears rotated by and having an axial movement withsaid rotor, a spring adapted to force the rotor and gears toward thefront of the pumping chamber, means for conducting discharge pressure tothe back of the rotor for, with said spring, forcing the rotor and gearstoward the front of the pumping chamber,

and means on the intake side permittin an unrestricted flow of fluid tothe front 0 the pumping chamber but preventing the escape of fluid backfrom the pumping chamber so as to keep the fluid pressure on the frontof the rotor substantially the same as the fluid pressure on the back ofthe rotor when the compressor is idle and thereby lower the startingtorque of the compressor.

8. A rotary compressor comprising a casing containing a pumping chamberwith an intake to and a discharge from said chamber, a rotor rotatablein and having an axial movement in said chamber, intermeshing internaland external pumping gears rotated by and having an axial movement withsaid rotor, said gears being located on the front take side permittingan unrestricted flow of v fluid to the pumping chamber but preventng theescape of fluid back from the pumpmg chamber so as to keep the pressureon the front for. the rotor substantially the same as on the back of therotor when the compressor is idle and thereby lower the starting torqueof the compressor.

9. A rotary compressor comprising a casng containing a umping chamberwith an lntake to and a ischarge from said chamber, intermeshinginternal and external pumping gears rotated in and having an axialmovement in said chamber, means for applying spring pressure anddischarge pressure to the back of the gears for forcing the gears towardthe front end of the pumping chamber, and means on the intake sidepermitting an unrestricted flow of fluid to the front of the pumpingchamber but preventing the escape of fluid back from the pumping chamberso as to keep the fluid pressure on the front of the gears substantiallythe same as the discharge pressure on the back of the gears when thecompressor is idle and thereby lower the starting torque of thecompressor.

10. A rotary compressor comprising acasing containing a pumping chamberwith an intake to and a discharge from said chamber and a cavitycommunicating with the back of said chamber, a rotor rotatable in andhaving an axial movement in said chamber, said rotor having a passagefrom'back to front, intermeshing internal and external pumping gearsrotated by and having an axial movement with said rotor, a spring insaid cavity adapted to force the rotor and gears toward the front of thepumping chamber, means for conducting discharge pressure to the back ofthe rotor for, with said spring, forcing the rotor and gears toward thefront of the pumping chamber, and means on the'intake side permitting anunrestricted flow of fluid to the front of the pumping chamber butpreventing the escape of fluid back from the pumping chamber so as tokeep the fluid pressure on the front of the rotor substantially the sameas the fluid pressure on the back of the rotor when the compressor isidle and thereby lower the starting torque of the compressor.

EBENEZER HILL.

